An online pamphlet of unknown origin purporting to represent the Islamic State surfaced Saturday on numerous social media accounts belonging to Palestinians and Israeli Arabs.

The digital poster, replete with official IS logos, claims Nashat Melhem, the assailant behind last weekend’s Tel Aviv pub shooting, was “one of the supporters of the caliphate in occupied Palestine.”

Melhem was killed after raising a weapon to police forces in his hometown in northern Israel on Friday.

Continued the poster, translated from Arabic into English by Breitbart Jerusalem:

The supporters of the Caliphate in the 1948 occupied territories consider the lion, Nashat Melhem, as a martyr going to Allah (may Allah accept him as a Shaheed).

He was one of the supporters of the caliphate in occupied Palestine…. He went to the sky a martyr after an exchange of fire with a special Jewish unit…Do not forget him when you pray.

Alongside the official IS logo, the pamphlet was signed by an unknown group, “The Caliphate in the 1948 Territories in Occupied Palestine.”

Israel’s security establishment is treating the pamphlet with cautious skepticism and is looking into the origin of the online message.

The Israeli news media largely did not cover the pamphlet with the exception of the Hebrew edition of Ynetnews, the country’s leading online news site.

There are significant questions about Melhem’s attack, his motivation and whether he was a member of any organized terrorist organization, such as the Islamic State.

Melhem was known to the security establishment here prior to the Tel Aviv shooting. He was jailed for five years for a 2007 attack on an Israeli soldier in which he attempted to grab the soldier’s rifle after assaulting the victim with a screwdriver.

Last week, Breitbart Jerusalem quoted one top Islamic State-aligned militant rejoicing at the possibility that the perpetrator was inspired by IS ideology while claiming his group never heard of Melhem prior to the attack.

“We hope it will emerge that the brother who carried out the operation will turn out to be a fighter for IS, or at least inspired by it, like the American couple [who carried out last month’s shooting in San Bernardino, California],” Abu al-Ayna Al-Ansari, a jihadi leader in Gaza affiliated with IS ideology, told Breitbart Jerusalem.

Israeli and Palestinian security services have clamped down on cells of Salafists in recent weeks who reportedly joined the Islamic State. Some of those extremists were Israeli Arabs from northern Israel.

Israel’s Shin Bet security agency in December announced the arrest of Israeli Arab youths from Nazareth for declaring allegiance to the Islamic State. The Shin Bet said that during interrogations “it emerged that, in the past year, the youths obtained firearms and trained with them, while becoming more devout during meetings they held. They expressed support for ISIS [Islamic State], and praised the jihad against infidels.”

Two weeks ago, two cousins accused of being Islamic State operatives were arrested in the Nazareth area on suspicion of plotting attacks in northern Israel.

The same night as Melhem’s attack, Salafists in the Gaza Strip allied with IS ideology claimed responsibility for firing 5 rockets form Gaza into southern Israel.

Melhem’s attack also happens to follow a call-to-arms broadcast two weeks ago by Abu Bakr al-Baghdadi, leader of the self-declared Islamic State, who threatened in a rare audio recording to turn Israel into a “graveyard.”